Ferrite ceramic composition, ceramic electronic component, and process for producing ceramic electronic component

ABSTRACT

This disclosure provides a ferrite ceramic composition, a ceramic electronic component including the ceramic composition, and a process of producing a ceramic electronic component including the ferrite ceramic composition, of which the insulation performance can be secured even when fired simultaneously with a metal wire material containing Cu as the main component, and which can have good electric properties. The ferrite ceramic composition includes an Ni—Mn—Zn-based ferrite having a molar content of CuO of 5 mol % or less and in which, when the molar content (x) of Fe 2 O 3  and the molar content (y) of Mn 2 O 3  are expressed by a coordinate point (x,y), the coordinate point (x,y) is located in an area bounded by coordinate points A (25,1), B (47,1), C (47,7.5), D (45,7.5), E (45,10), F (35,10), G (35,7.5) and H (25,7.5).

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority to Japanese Patent ApplicationNo. 2011-192021 filed on Sep. 2, 2011, the entire contents of thisapplication being incorporated herein by reference in its entirety.

TECHNICAL FIELD

The technical field relates to a ferrite ceramic composition, a ceramicelectronic component, and a process for producing a ceramic electroniccomponent, and more specifically relates to a ferrite ceramiccomposition which can be fired simultaneously with an electricallyconductive material containing Cu as the main component, a ceramicelectronic component (e.g., a chip-type inductor) which is producedusing the ferrite ceramic composition, and a process for producing theceramic electronic component.

BACKGROUND

In recent years, ceramic electronic components have been used widely invarious fields, and chip-type inductors have been used widely as filtersfor high frequency applications that can remove noises generated inelectronic devices such as mobile phones and notebook-size personalcomputers.

As for the processes for producing this type of chip-type inductor,various processes are known. For example, JP 7-22266 A (claim 1, claim2, paragraph Nos. [0007], [0017], etc.) proposes a process for producingan inductor element, which comprises: repeating a step, which comprisesprinting a ferrite paste containing an organic binder on a substrate anddrying the printed ferrite paste, multiple times, thereby forming afirst ferrite green sheet layer; placing a metal conductive body on thefirst ferrite green sheet layer; repeating a step, which comprisesprinting the ferrite paste on the first ferrite green sheet layer andthe metal conductive body and drying the printed ferrite paste, multipletimes, thereby forming a second ferrite green sheet layer on the firstferrite green sheet layer and the metal conductive body; compressing thefirst ferrite green sheet layer, the metal conductive body and thesecond ferrite green sheet layer together; and firing the compressedproduct.

In JP 7-22266 A (claim 1, claim 2, paragraph Nos. [0007], [0017], etc.),it is described that one metal selected from Ag, Pd, Pt, Ni and Cu or analloy of at least two metals selected from the above-mentioned metals isused as the metal conductive body.

In JP 7-22266 A (claim 1, claim 2, paragraph Nos. [0007], [0017], etc.),it is contemplated to produce a high-quality chip-type inductor within ashort time and without causing any structural defect and so on byemploying the above-mentioned process.

JP 2001-52946 A (claim 1, paragraph Nos. [0014], [0026], etc.) proposesa process for producing a chip-type inductor, which comprises the stepsof: inserting a conductive wire comprising a metal wire into a moldingmold, holding both ends of the conductive wire by a support sectionformed inside of the molding mold to position the conductive wire at thecenter of the molding mold; injecting a magnetic ceramic slurry into themolding mold; molding the ceramic slurry that has been injected into themolding mold by a wet-mode pressing technique to form a molding havingthe conductive wire embedded therein; firing the molding to produce amagnetic core; and forming external electrodes, which are respectivelyconnected to both ends of the conductive wire, at both end surfaces ofthe fired magnetic core.

In JP 2001-52946 A (claim 1, paragraph Nos. [0014], [0026], etc.), it isdescribed that Ag, Cu or an alloy of either one of these metals is usedas the conductive wire.

In JP 2001-52946 A (claim 1, paragraph Nos. [0014], [0026], etc.), it iscontemplated to produce a high-density and high-quality chip-typeinductor by producing the molding having the conductive wire embeddedtherein by a wet-mode pressing technique.

SUMMARY

The present disclosure provides a ferrite ceramic composition, a ceramicelectronic component including the ceramic composition, and a process ofproducing a ceramic electronic component including the ferrite ceramiccomposition of which the insulation performance can be secured even whenfired simultaneously with a metal wire material containing Cu as themain component and which can exhibit good electric properties.

In one aspect of the disclosure, a ferrite ceramic composition comprisesat least Fe, Mn, Ni and Zn, where in ferrite ceramic composition, amolar content of Cu is 0 to 5 mol % in terms of CuO content, and ischaracterized in that, when a molar content (x (mol %)) of Fe in termsof Fe₂O₃ content and a molar content (y (mol %)) of Mn in terms of Mn₂O₃content are expressed by a coordinate point (x,y), the coordinate point(x,y) is located in an area bounded by coordinate points A (25,1), B(47,1), C (47,7.5), D (45,7.5), E (45,10), F (35,10), G (35,7.5) and H(25,7.5).

In a more specific embodiment of the ferrite ceramic composition, amolar content of Zn may be 33 mol % or less in terms of ZnO content.

In another more specific embodiment of the ferrite ceramic composition,a molar content of Zn may be 6 mol % or more in terms of ZnO content.

In another aspect of the disclosure, a ceramic electronic componentincludes a magnetic body part and a metal wire material embedded in themagnetic body part, and is characterized in that the metal wire materialcomprises an electrically conductive material containing Cu as the maincomponent and the magnetic body part comprises any one of theabove-mentioned ferrite ceramic compositions.

In a more specific embodiment of the ceramic electronic component, themetal wire material may have a linear shape.

In another more specific embodiment of the ceramic electronic component,the metal wire material may have a spiral shape.

In yet another more specific embodiment of the ceramic electroniccomponent, the magnetic body part may be fired in an atmosphere havingan oxygen partial pressure equal to or lower than the equilibrium oxygenpartial pressure for Cu—Cu₂O.

In another aspect of the present disclosure, a process for producing aceramic electronic component includes a calcination step of weighing anFe compound, an Mn compound, a Cu compound, a Zn compound and an Nicompound precisely in such a manner that a molar content of Cu becomes 0to 5 mol % in terms of CuO content and, when a molar content (x (mol %))of Fe in terms of Fe₂O₃ content and a molar content (y (mol %)) of Mn interms of Mn₂O₂ content are expressed by a coordinate point (x,y), thecoordinate point (x,y) can be located in an area bounded by coordinatepoints A (25,1), B (47,1), C (47,7.5), D (45,7.5), E (45,10), F (35,10),G (35,7.5) and H (25,7.5), mixing the weighed compounds together, andcalcining the resultant mixture, thereby producing a calcined powder.The process includes a ceramic thin layer body production step ofproducing ceramic thin layer bodies from the calcined powder, a laminateformation step of laminating the multiple ceramic thin layer bodies oneach other in such a manner that a metal wire material containing Cu asthe main component and having a linear shape is intercalated between atleast a pair of the ceramic thin layer bodies, thereby forming alaminate, and a firing step of firing the laminate in a firingatmosphere having an oxygen partial pressure equal to or lower than theequilibrium oxygen partial pressure for Cu—Cu₂O.

In still another aspect of the present disclosure, a process forproducing a ceramic electronic component includes a calcination step ofweighing an Fe compound, an Mn compound, a Cu compound, a Zn compoundand an Ni compound precisely in such a manner that a molar content of Cubecomes 0 to 5 mol % in terms of CuO content and, when a molar content(x (mol %)) of Fe in terms of Fe₂O₃ content and a molar content (y (mol%)) of Mn in terms of Mn₂O₃ content are expressed by a coordinate point(x,y), the coordinate point (x,y) can be located in an area bounded bycoordinate points A (25,1), B (47,1), C (47,7.5), D (45,7.5), E (45,10),F (35,10), G (35,7.5) and H (25,7.5), mixing the weighed compoundstogether, and calcining the resultant mixture, thereby producing acalcined powder. The process further includes ferrite paste productionstep of producing a ferrite paste from the calcined powder, a moldingproduction step of placing a metal wire material containing Cu as themain component in a mold, then injecting the ferrite paste into the moldand carrying out a molding treatment to produce a molding, and a firingstep of firing the molding in a firing atmosphere having an oxygenpartial pressure equal to or lower than the equilibrium oxygen partialpressure for Cu—Cu₂O.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a view illustrating the content ranges of Fe₂O₃ and Mn₂O₃ forthe ferrite ceramic composition according to an exemplary embodiment.

FIG. 2 is a perspective view illustrating an embodiment (a firstembodiment) of a chip-type inductor as the ceramic electronic componentaccording an exemplary embodiment.

FIG. 3 is a cross sectional view of FIG. 2 taken along line A-A.

FIG. 4 is an exploded perspective view illustrating the main part of thefirst exemplary embodiment.

FIG. 5 is a perspective view illustrating a second exemplary embodimentof a chip-type inductor as a ceramic electronic component.

FIG. 6 is a vertical sectional view of FIG. 5.

FIG. 7 is a cross sectional view illustrating the main part of theproduction process of the second exemplary embodiment.

FIG. 8 is a cross sectional view of a sample for use in the specificresistance measurement, which is produced in Example 1.

FIG. 9 is a view illustrating the impedance property of a sampleproduced in Example 2, together with the impedance property of a sampleof a comparative example which is out of the scope of the presentdisclosure.

DETAILED DESCRIPTION

In JP 7-22266 A (claim 1, claim 2, paragraph Nos. [0007], [0017], etc.),Ag, Pd, Pt, Ni, Cu, or an alloy of any one of these elements is used.However, when a noble metal material such as Ag, Pd, and Pt is used,such a problem occurs that the material cost is increased andproductivity is deteriorated.

Generally, an Ni—Zn-based ferrite is fired in an air atmosphere.However, when a poor metal material such as Ni and Cu is used as a metalwire material, the metal wire material might be oxidized during thefiring in an air atmosphere.

Meanwhile, when the ferrite material having the poor metal materialembedded therein is fired in a reductive atmosphere for the purpose ofavoiding the oxidation of the poor metal material, Fe₂O₃ contained inthe ferrite material is reduced into Fe₃O₄, which might result in thedecrease in a specific resistance ρ.

Thus, in a case where Cu is used as a metal wire material and a magneticmaterial sheet having the metal wire material embedded therein is firedat a temperature of 800° C. or higher, when the firing is performed inan oxidative atmosphere having such an oxygen partial pressure that thestate of Fe₂O₃ can be maintained, Cu is also oxidized to form Cu₂O. Onthe other hand, when the firing is performed in a reductive atmospherehaving such an oxygen partial pressure that the state of metal Cu can bemaintained, Fe₂O₃ is reduced to form Fe₃O₄.

From the relationship between the equilibrium oxygen partial pressurefor Cu—Cu₂O and the equilibrium oxygen partial pressure for Fe₂O₃—Fe₂O₄,it is known that there is not any area in which Cu and Fe₂O₃ can coexistat a temperature of 800° C. or higher.

The same is almost true with respect to the relationship between theequilibrium oxygen partial pressure for Ni—NiO and the equilibriumoxygen partial pressure for Fe₂O₃—Fe₃O₄.

Therefore, in JP 7-22266 A (claim 1, claim 2, paragraph Nos. [0007],[0017], etc.), although the poor metal material such as Cu and Ni andthe ferrite material are fired simultaneously in a reductive atmosphere,when the firing is performed in such a reductive atmosphere that thepoor metal material is not oxidized, Fe₂O₃ is reduced into Fe₂O₄ andconsequently the specific resistance ρ is decreased, which might resultin the deterioration in electric properties including an impedanceproperty, because there is not any area in which the poor metal materialand Fe₂O₃ can coexist.

The present inventors have made intensive studies on ferrite materialshaving a spinel-type crystal structure represented by general formulaX₂O₃.MeO (wherein X represents Fe or Mn; and Me represents Zn, Cu orNi). As a result, it is found, when the molar content of CuO is set to 5mol % or less and the amounts of Fe₂O₃ and Mn₂O₂ added are limitedwithin specified ranges in the ferrite material, desired good insulationperformance can be achieved even if the ferrite material is firedsimultaneously with a Cu-based material, and it becomes possible toproduce a ceramic electronic component having good electric properties.

As a result of the further intensive studies made by the presentinventors, it is found that, although it is preferred to add ZnO to theferrite magnetic composition for the purpose of achieving more superiorproperties, the Curie point (Tc) is decreased, the operation at highertemperature cannot be ensured and reliability may be deteriorated whenthe content of ZnO exceeds 33 mol %.

Exemplary embodiments of the present disclosure that can address theabove drawbacks will not be described in detail.

One exemplary embodiment of the ferrite ceramic composition has aspinel-type crystal structure represented by general formula X₂O₃.MeO,and contains at least Fe₂O₃ and Mn₂O₃ which are trivalent elementcompounds and ZnO and NiO which are bivalent element compounds, andoptionally contains CuO which is a bivalent element compound.

Specifically, the ferrite ceramic composition contains CuO at a molarcontent of 0 to 5 mol %, also contains Fe₂O₃ and Mn₂O₃ at such molarcontents that, when the molar content of Fe₂O₃ is expressed by x (mol%), the molar content of Mn₂O₃ is expressed by y (mol %) and the molarcontent of Fe₂O₃ and the molar content of Mn₂O₃ are expressed by acoordinate point (x,y), the coordinate point (x,y) is located within ashaded area (X) defined by points A to H, as shown in FIG. 1, whereinthe remainder is made up by ZnO and NiO.

The coordinate points (x,y) for the coordinate points A to H correspondto the following molar contents: A (25,1), B (47,1), C (47,7.5), D(45,7.5), E (45,10), F (35,10), G (35,7.5), and H (25,7.5).

Next, the reason why the molar contents of CuO, Fe₂O₃ and Mn₂O₂ aredefined within the above-mentioned ranges is described in detail.

(1) The Molar Content of CuO:

With respect to an Ni—Zn-based ferrite, when CuO, which has a meltingpoint of as low as 1,026° C., is added to the ferrite ceramiccomposition, the ferrite magnetic composition can be fired at a lowertemperature and the sintering properties can be improved.

On the other hand, when a Cu-based material containing Cu as the maincomponent and a ferrite material are fired simultaneously, if the firingis performed in an air atmosphere, Cu is oxidized readily to form Cu₂O.Therefore, it is required to perform the firing in such a reductiveatmosphere that the oxidation of Cu does not occur.

However, when the firing is performed in such a reductive atmosphere, ifthe molar content of CuO exceeds 5 mol %, CuO in the ferrite rawmaterial is reduced to form Cu₂O and the amount of Cu₂O in the ferriteraw material is increased, which might result in the decrease in aspecific resistance ρ.

Then, in the embodiment, the amount of CuO to be added is controlled insuch a manner that the molar content of CuO becomes 5 mol % or less,i.e., 0 to 5 mol %.

(2) The Molar Contents of Fe₂O₃ and Mn₂O₂:

The content of Fe₂O₃ in the composition is smaller than the contentdefined in the stoichiometric composition, and Mn₂O₂ is contained bysubstituting a portion of Fe by Mn, whereby the decrease in a specificresistance ρ can be avoided and insulation performance can be improved.

That is, in the case of a spinel-type crystal structure (general formulaX₂O₂.MeO), the ratio of X₂O₃ (wherein X: Fe, Mn) to MeO (wherein Me: Ni,Zn, Cu) is 50:50 according to the stoichiometric composition, and X₂O₃and MeO are added at contents substantially defined in thestoichiometric composition.

When a Cu-based material containing Cu as the main component and theferrite material are fired simultaneously, if the firing is performed inan air atmosphere, Cu is oxidized readily to form Cu₂O. Therefore, it isrequired to perform the firing in such a reductive atmosphere that theoxidation of Cu does not occur. On the other hand, if Fe₂O₃, which isthe main component of the ferrite material, is fired in a reductiveatmosphere, Fe₂O₄ is formed. Therefore, with respect to Fe₂O₃, it isrequired to perform the firing in an oxidative atmosphere.

However, as stated above, it is known that there is not any area inwhich both metal Cu and Fe₂O₃ can coexist when the firing is performedat a temperature of 800° C. or higher, from the relationship between theequilibrium oxygen partial pressure for Cu—Cu₂O and the equilibriumoxygen partial pressure for Fe₂O₄—Fe₂O₃.

Thus, in a temperature region of 800° C. or higher, a reductiveatmosphere for Mn₂O₃ can be achieved at a higher oxygen partial pressurethan that for Fe₂O₃. Therefore, at an oxygen partial pressure that isequal to or lower than the equilibrium oxygen partial pressure forCu—Cu₂O, the atmosphere for Mn₂O₃ becomes strongly reductive comparedthat for Fe₂O₃. Therefore, the firing can be accomplished while reducingMn₂O₃ preferentially. That is, since Mn₂O₃ is reduced preferentiallythan Fe₂O₃, the firing treatment can be accomplished before Fe₂O₃ isreduced into Fe₃O₄.

As stated above, when the molar content of Fe₂O₃ is smaller than thatdefined in the stoichiometric composition and Mn₂O₃, which is atrivalent element compound like Fe₂O₃, is added to the ferrite ceramiccomposition, even if a Cu-based material and the ferrite material arefired simultaneously at an oxygen partial pressure equal to or lowerthan the equilibrium oxygen partial pressure for Cu—Cu₂O, Mn₂O₃ isreduced preferentially and, therefore, the sintering can be accomplishedbefore the occurrence of the reduction of Fe₂O₃. Therefore, it becomespossible to allow metal Cu and Fe₂O₃ to coexist more effectively. As aresult, the decrease in a specific resistance ρ can be avoided andinsulation performance can be improved.

If the molar content of Fe₂O₃ is less than 25 mol %, the molar contentof Fe₂O₃ is decreased excessively. As a result, the specific resistanceρ is decreased and desired insulation performance cannot be secured anymore.

If the molar content of Mn₂O₃ is less than 1 mol %, the molar content ofMn₂O₃ is reduced excessively, and therefore Fe₂O₃ can be reduced intoFe₃O₄ more readily. As a result, the specific resistance ρ is decreasedand satisfactory insulation performance cannot be secured.

If the molar content of Fe₂O₃ exceeds 47 mol %, the molar content ofFe₂O₃ becomes excessive. In this case, Fe₂O₃ can also be reduced intoFe₃O₄ more readily. As a result, the specific resistance ρ is decreasedand satisfactory insulation performance cannot be secured.

If the molar content of Mn₂O₃ exceeds 10 mol %, a satisfactorily highspecific resistance ρ cannot be achieved and insulation performancecannot be secured.

Further, in the case where the molar content of Fe₂O₃ is 25 mol % ormore but is less than 35 mol %, and in the case where the molar contentof Fe₂O₃ is 45 mol % or more but less than 47 mol %, if the molarcontent of Mn₂O₃ exceeds 7.5 mol %, the decrease in a specificresistance ρ is caused and desired insulation performance cannot besecured.

Then, in this embodiment, the molar contents of Fe₂O₃ and Mn₂O₃ arecontrolled so as to fall within the area bounded by the coordinatepoints A to H shown in FIG. 1.

In the ferrite ceramic composition, the molar contents of ZnO and NiOare not particularly limited and can be set properly in accordance withthe molar contents of Fe₂O₃, Mn₂O₃ and CuO. Preferably, ZnO and NiO areadded in such a manner that the molar content of ZnO becomes 6 to 33 mol% and the remainder is made up by NiO.

If the molar content of ZnO exceeds 33 mol %, the Curie point (Tc) isdecreased and the operation at higher temperatures may not be ensured.Therefore, the content of ZnO is preferably 33 mol % or less.

ZnO has an effect of improving a magnetic permeability (μ). Forachieving the effect, it is needed to add ZnO at a molar content of 6mol %.

For the reasons stated above, the molar content of ZnO is preferably 6to 33 mol %.

As stated above, the ferrite ceramic composition has a molar content ofCu of 0 to 5 mol % in terms of CuO content, and also has such molarcontents of Fe and Mn that, when the molar content (x (mol %)) of Fe interms of Fe₂O₃ content and the molar content (y (mol %)) of Mn in termsof Mn₂O₃ content are expressed by a coordinate point (x,y), thecoordinate point (x,y) is located within an area bounded by thecoordinate points A to H. Therefore, when the ferrite ceramiccomposition is fired simultaneously with a Cu-based material, thespecific resistance ρ is not decreased and desired insulationperformance can be secured.

Specifically, such good insulation performance that a specificresistance ρ of 10⁷ Ω-cm or more can be achieved. Consequently, itbecomes possible to produce a desired ceramic electronic componenthaving good electric properties including an impedance property.

In the ferrite ceramic composition, since the molar content of Zn is 6to 33 mol % in terms of ZnO content, good magnetic permeability can beachieved and a satisfactory Curie point can be secured. The compositionenables the production of a ceramic electronic component which can beoperated under conditions including a high operation temperature.

Next, a ceramic electronic component produced using the ferrite ceramiccomposition is described in detail with reference to FIGS. 2 to 7.

FIG. 2 is a perspective view illustrating one exemplary embodiment (afirst embodiment) of a laminated inductor as the ceramic electroniccomponent according to the present disclosure, and FIG. 3 is a crosssectional view of FIG. 2 taken along line A-A.

In the laminated inductor, a component body (1) comprises a magneticbody part (2) and a metal wire material (3) embedded in the magneticbody part (2). At both ends of the component body (1), externalelectrodes (4 a, 4 b) are formed.

The metal wire material (3) is formed in a linear shape and is embeddedin substantially the longitudinal direction center of the magnetic bodypart (2), and both ends of the metal wire material (3) are electricallyconnected to the external electrodes (4 a, 4 b), respectively.

In the first exemplary embodiment, the metal wire material (3) comprisesan electrically conductive material containing Cu as the main component,and the magnetic body part (2) comprises the above-mentioned ferriteceramic composition according to the present disclosure.

By employing this constitution, the oxidation of Cu or the reduction ofFe₂O₃ can be avoided. Therefore, a good specific resistance ρ can besecured and a laminated inductor having desired good electric propertiescan be produced.

Specifically, the specific resistance ρ can be improved to 10⁷ Ω·cm ormore, and a laminated inductor that has a high impedance value in aspecific frequency range and is suitable for the absorption of noisescan be produced.

FIG. 4 is an exploded perspective view of the component body (1), and anexemplary process for producing the laminated inductor is now describedin detail with reference thereto.

First, Fe₂O₃, ZnO, NiO, and optionally CuO are provided as the ceramicraw materials. The ceramic raw materials are weighed precisely so as tohave a CuO content of 0 to 5 mol % and such Fe₂O₃ and Mn₂O₃ contentsthat the contents of Fe₂O₃ and Mn₂O₃ fulfill the specified area boundedby the coordinate points A to H of FIG. 1.

Subsequently, the precisely weighed materials are introduced into a potmill together with pure water and cobbled stones such as PSZ (partiallystabilized zirconia) balls, the mixture is fully mixed and milled in awet mode, and the milled product is evaporated to dryness and thencalcined at a temperature of 700 to 800° C. for a predetermined time.

Subsequently, the calcined powder is introduced into the pot mill againtogether with an organic binder such as polyvinyl butyral, an organicsolvent such as ethanol, and toluene and PSZ balls, and the resultantmixture is fully mixed and milled, thereby producing a ceramic slurry.

Subsequently, the ceramic slurry is molded into a sheet-like formemploying a doctor blade method or the like, thereby producing amagnetic ceramic green sheet (a ceramic thin layer body; simply referredto as “a magnetic material sheet”, hereinafter) (5) having apredetermined thickness.

Subsequently, multiple pieces of the multiple magnetic material sheets(5) are laminated on each other to form a first magnetic material layer(6 a), and a metal wire material (3) having a diameter of about 50 to100 μm is arranged on the upper surface of the first magnetic materiallayer (6 a) in parallel with the side surfaces of the first magneticmaterial layer (6 a) at substantially the center parts of the both endsurfaces. On the first magnetic material layer (6 a) and the metal wirematerial (3), multiple pieces of the multiple magnetic material sheets(5) are laminated, thereby forming a second magnetic material layer (6b). The resultant laminate is pressurized and compressed, and is thencut into a predetermined size, thereby producing a laminated molding.

Subsequently, the laminated molding is fully defatted by heating in anatmosphere that does not cause the oxidation of Cu. The defattedlaminated molding is fed into a firing furnace of which the atmospherehas been controlled with an N₂—H₂—H₂O mixed gas so as to have an oxygenpartial pressure equal to or lower than the equilibrium oxygen partialpressure for Cu—Cu₂O, and is then fired at 900 to 1,050° C. for apredetermined time, thereby producing a component body (1) in which themetal wire material (3) is embedded in the magnetic body part (2).

Subsequently, an electrically conductive paste for external electrodeswhich contains Cu or the like as the main component is applied to bothends of the component body (1). The electrically conductive paste isdried and then baked at 900° to form external electrodes (4 a, 4 b). Inthis manner, the above-mentioned laminated inductor can be produced.

As mentioned above, the first embodiment comprises: a calcination stepof weighing an Fe compound, an Mn compound, a Cu compound, a Zn compoundand an Ni compound precisely in such a manner that the molar content ofCu becomes 0 to 5 mol % in terms of CuO content and, when the molarcontent (x (mol %)) of Fe in terms of Fe₂O₃ content and the molarcontent (y (mol %)) of Mn in terms of Mn₂O₃ content are expressed by acoordinate point (x,y), the coordinate point (x,y) can be located in thespecified area bounded by coordinate points A to H (see FIG. 1), mixingthe weighed compounds together, and calcining the resultant mixture,thereby producing a calcined powder; a magnetic material sheetproduction step of producing magnetic material sheets (5) from thecalcined powder; a laminate formation step of laminating multiple piecesof the magnetic material sheets (5) on each other in such a manner thata metal wire material (3) containing Cu as the main component and havinga linear shape is intercalated between at least a pair of the magneticmaterial sheets (5), thereby forming a laminate; and a firing step offiring the laminate in a firing atmosphere having an oxygen partialpressure equal to or lower than the equilibrium oxygen partial pressurefor Cu—Cu₂O. Therefore, even when the ceramic material is fired under afiring atmosphere having an oxygen partial pressure equal to or lowerthan the equilibrium oxygen partial pressure for Cu—Cu₂O together withthe linear metal wire material (3) containing Cu as the main component,it becomes possible to produce an inductor having good insulationperformance and good electric properties without undergoing theoxidation of Cu or the reduction of Fe.

FIG. 5 is a perspective view illustrating an inductor which is a secondexemplary embodiment of a ceramic electronic component according to thepresent disclosure, and FIG. 6 is a cross sectional view of FIG. 5.

The inductor is substantially the same as the first exemplaryembodiment, and the component body (11) comprises a magnetic body part(12) and a metal wire material (13) embedded in the magnetic body part(12). At both ends of the component body (11), external electrodes (14a, 14 b) are formed.

That is, the metal wire material (13) is formed in a spiral shape and isembedded in substantially the longitudinal direction center of themagnetic body part (12), and both ends of the metal wire material (13)are electrically connected to the external electrodes (14 a, 14 b),respectively.

In the second exemplary embodiment, since the metal wire material (13)has a spiral shape, it becomes possible to produce an inductor having ahigher inductance value compared with that of the first embodiment inwhich a metal wire material having a linear shape is used.

In the second exemplary embodiment, the metal wire material (13) is alsocomposed of an electrically conductive material containing Cu as themain component and the magnetic body part (12) is also composed of theabove-mentioned ferrite ceramic composition according to the presentdisclosure. By employing this constitution, even when the magnetic bodypart (12) is fired in such a state that the metal wire material (13) isembedded in the magnetic body part (12), the occurrence of the oxidationof Cu or the reduction of Fe₂O₃ can be avoided and therefore a goodspecific resistance ρ can be secured. Therefore, it becomes possible toproduce a ceramic electronic component having desired good electricproperties.

Next, the process for producing the inductor is described in detail.

First, a calcined power is produced by the same methods and proceduresas those employed in the first embodiment.

Subsequently, the calcined powder is mixed with an organic vehiclecomprising a resin such as an ethyl cellulose resin and an organicsolvent such as terpineol, and the mixture is kneaded using a tripleball mill, thereby producing a ferrite paste.

Subsequently, a molding treatment is performed using a mold.

FIG. 7 is a cross sectional view of a molding apparatus. That is, themolding apparatus (15) comprises an upper mold (18) having a firstcavity (16) and a paste injection port (17) and a lower mold (20) havinga second cavity (19).

A metal wire material (13) containing Cu as the main component andshaped into a spiral form is latched in a support groove (not shown) inthe lower mold (20) to tightly adhere the metal wire material (13)between the upper mold (20) and the lower mold (20), the ferrite pasteis injected through the paste injection port (17), the molding apparatus(15) is heated while applying a pressure to evaporate and remove theorganic solvent, thereby producing a molding.

Subsequently, the molding is removed from the molding apparatus (15).The molding is fully defatted by heating under an atmosphere that doesnot cause the oxidation of Cu, is then fed into a firing furnace ofwhich the atmosphere has been adjusted with an N₂—H₂—H₂O mixed gas so asto have an oxygen partial pressure equal to or lower than theequilibrium oxygen partial pressure for Cu—Cu₂O, and is then fired at900 to 1,050° C. for a predetermined time. In this manner, a componentbody (11) in which the metal wire material (13) is embedded in themagnetic body part (12) can be produced.

Subsequently, an electrically conductive paste for external electrodeswhich contains Cu or the like as the main component is applied to bothends of the component body (11), is dried, and is then baked at 900° C.,thereby forming external electrodes (14 a, 14 b). In this manner, theabove-mentioned inductor can be produced.

In the second exemplary embodiment, substantially like the firstembodiment, even when the ferrite material is fired under a firingatmosphere having an oxygen partial pressure equal to or lower than theequilibrium oxygen partial pressure for Cu—Cu₂O together with thespiral-shaped metal wire material (13) containing Cu as the maincomponent, the oxidation of Cu or the reduction of Fe does not occur.Therefore, it becomes possible to produce an inductor having goodinsulation performance and good electric properties.

The present disclosure is not limited to the above-mentionedembodiments. For example, in the first exemplary embodiment, althoughthe ceramic green sheet (5) is produced from a calcined powder, anyother ceramic thin layer body may also be used. For example, a magneticcoating film may be formed on a PET film by a printing treatment.

Further, in the second exemplary embodiment, although a metal wirematerial (13) having a spiral shape is used, the shape of the metal wirematerial (13) is not particularly limited and a prismatic shape, aflattened shape or the like, of course, may also be employed.

As a matter of course, the ferrite ceramic composition according to thepresent disclosure can be used for various types of inductors, can alsobe used widely for use applications in which the ferrite ceramiccomposition is fired simultaneously with an electrically conductivematerial containing Cu as the main component, and can also be used forother ceramic electronic components.

More specific examples of the present disclosure will now be described.

Example 1

Fe₂O₃, Mn₂O₃, ZnO, CuO and NiO were provided as ceramic raw materials,and the ceramic raw materials were weighed precisely so that the molarcontents of the ceramic raw materials became those shown in Tables 1 to3. That is, the ceramic raw materials were weighed precisely in such amanner that the contents of ZnO and CuO were fixed to 30 mol % and 1 mol%, respectively, the molar content of each of Fe₂O₃ and Mn₂O₃ was variedand the remainder was made up by NiO.

Next, the precisely weighed materials were placed in a pot mill made ofvinyl chloride together with pure water and PSZ balls, the mixture wasfully mixed and milled in a wet mode, the resultant mixture wasevaporated to dryness, and the dried product was calcined at 750° C.,thereby producing a calcined powder.

Subsequently, the calcined powder was placed again in the pot mill madeof vinyl chloride together with a polyvinyl butyral binder (an organicbinder), ethanol (an organic solvent) and PSZ balls, and the mixture wasfully mixed and milled, thereby producing a ceramic slurry.

Subsequently, the ceramic slurry was shaped into a sheet-like formhaving a thickness of 25 μm employing a doctor blade method, and thesheet-like material was then punched out into a size of 50 mm in lengthand 50 mm in width. In this manner, a magnetic material sheet wasproduced.

Subsequently, multiple pieces of the magnetic material sheets thusproduced were laminated in such a manner that the total thickness became1.0 mm, the resultant laminate was heated to 60° C., then compressed for60 seconds at a pressure of 100 MPa, and then punched out into a ringshape having an outer diameter of 20 mm and an inner diameter of 12 mm.In this manner, a ceramic molding was produced.

Subsequently, the resultant ceramic molding was fully defatted byheating. An N₂—H₂—H₂O mixed gas was fed to a firing furnace to adjustthe oxygen partial pressure in the firing furnace to 6.7×10⁻² Pa, andthen the ceramic molding was introduced into the firing furnace andfired at 1,000° C. for 2 hours. In this manner, a ring-shaped sample wasproduced.

The oxygen partial pressure of 6.7×10⁻² Pa is the equilibrium oxygenpartial pressure for Cu—Cu₂O at 1,000° C. The ceramic molding was firedfor 2 hours under the equilibrium oxygen partial pressure for Cu—Cu₂O.In this manner, ring-shaped samples Nos. 1 to 104 were produced.

A soft copper wire was wound around each of the ring-shaped samples Nos.1 to 104 20 turns, the inductance of the resultant product was measuredat a measurement frequency of 1 MHz using an impedance analyzer (AgilentTechnologies, E4991A), and a magnetic permeability (i) was determinedfrom the measurement value.

Subsequently, an organic vehicle comprising terpineol (an organicsolvent) and an ethyl cellulose resin (a binder resin) was mixed with aCu powder, and the mixture was kneaded with a triple roll mill. In thismanner, a Cu paste was produced.

Subsequently, the Cu paste was screen-printed on the surface of themagnetic material sheet, thereby producing an electrically conductivefilm having a predetermined pattern on the magnetic material sheet. Apredetermined number of the magnetic material sheets each having theelectrically conductive film formed thereon were laminated in apredetermined order. The resultant laminate was intercalated between themagnetic material sheets on each of which the electrically conductivefilm was not formed, and the resultant laminate was compressed and thencut into a predetermined size. In this manner, a laminated molding wasproduced.

Subsequently, the laminated molding was defatted sufficiently, anN₂—H₂—H₂O mixed gas was fed to a firing furnace to adjust the oxygenpartial pressure in the firing furnace to 6.7×10⁻² Pa (the equilibriumoxygen partial pressure for Cu—Cu₂O at 1,000° C.). The laminated moldingwas introduced into the firing furnace, and was then fired at 1,000° C.for 2 hours. In this manner, a sintered ceramic body having an internalelectrode embedded therein was produced.

Subsequently, the sintered ceramic body was introduced into a pottogether with water, and the sintered ceramic body was subjected to abarrel treatment using a centrifugal barrel machine. In this manner, aceramic body was produced.

An electrically conductive paste for external electrodes which containsCu or the like as the main component, was applied to both ends of theceramic body, and was then dried. The resultant product was subjected toa baking treatment at 750° C. in a firing furnace of which the oxygenpartial pressure was adjusted to 4.3×10⁻³ Pa. In this manner, samplesfor specific resistance measurement Nos. 1 to 104 were produced. In thisexample, the oxygen partial pressure of 4.3×10⁻³ Pa is the equilibriumoxygen partial pressure for Cu—Cu₂O at 750° C.

Each of the specific resistance measurement samples had an outer size of3.0 mm in length, 3.0 mm in width and 1.0 mm in thickness.

FIG. 8 is a cross sectional view of each of the specific resistancemeasurement samples. In the ceramic body (51), internal electrodes (52 ato 52 d) were embedded in the magnetic material layer (53) in such amanner that the extraction sections were arranged in a staggeredconfiguration, and external electrodes (54 a, 54 b) were formed at bothends of the ceramic body (51).

Subsequently, with respect to the specific resistance measurementsamples Nos. 1 to 104, a voltage of 50 V was applied to each of theexternal electrodes (54 a, 54 b) for 30 seconds, and a current generatedupon the application of the voltage was measured. A resistivity wascalculated from the measurement value, and a logarithm log ρ for aspecific resistance (referred to as “a specific resistance log ρ,”hereinafter) was calculated from the outer size of each of the samples.

In Tables 1 to 3, the ferrite compositions and the measurement resultsfor samples Nos. 1 to 104 are shown.

TABLE 1 Electric properties Specific Sam- resistance Magnetic pleFerrite composition (mol %) logρ, permeability No. Fe₂O₃ Mn₂O₃ ZnO CuONiO ρ: Ω · cm μ (—)  1* 49 0 30 1 20 2.8 350  2* 49 1 30 1 19 3.3 400 3* 49 2 30 1 18 3.4 600  4* 49 5 30 1 15 3.4 750  5* 49 7.5 30 1 12.53.4 900  6* 49 10 30 1 10 3.4 1100  7* 49 13 30 1 7 3.3 1250  8* 49 1530 1 5 3.1 1450  9* 48 0 30 1 21 4.4 290 10* 48 1 30 1 20 5.9 330 11* 482 30 1 19 6.3 500 12* 48 5 30 1 16 6.1 640 13* 48 7.5 30 1 13.5 5.9 76014* 48 10 30 1 11 5.6 900 15* 48 13 30 1 8 5 1050 16* 48 15 30 1 6 4.31250 17* 47 0 30 1 22 5.3 235 18 47 1 30 1 21 7 260 19 47 2 30 1 20 7.5400 20 47 5 30 1 17 7.3 520 21 47 7.5 30 1 14.5 7 625 22* 47 10 30 1 126.4 750 23* 47 13 30 1 9 5.6 880 24* 47 15 30 1 7 4.9 1050 25* 46 0 30 123 5.9 195 26 46 1 30 1 22 7.4 215 27 46 2 30 1 21 7.6 320 28 46 5 30 118 7.5 430 29 46 7.5 30 1 15.5 7.3 520 30* 46 10 30 1 13 6.8 630 31* 4613 30 1 10 6 730 32* 46 15 30 1 8 5.2 880 33* 45 0 30 1 24 6.2 165 34 451 30 1 23 7.7 180 35 45 2 30 1 22 7.9 250 36 45 5 30 1 19 7.8 340 37 457.5 30 1 16.5 7.6 420 38 45 10 30 1 14 7.1 520 39* 45 13 30 1 11 6.3 60040* 45 15 30 1 9 5.4 720 *out of the scope of the disclosure (claim 1)

TABLE 2 Electric properties Specific Sam- resistance Magnetic pleFerrite composition (mol %) logρ, permeability No. Fe₂O₃ Mn₂O₃ ZnO CuONiO ρ: Ω · cm μ (—) 41* 44 0 30 1 25 6.4 145 42 44 1 30 1 24 7.9 155 4344 2 30 1 23 8 210 44 44 5 30 1 20 8 280 45 44 7.5 30 1 17.5 7.8 340 4644 10 30 1 15 7.3 420 47* 44 13 30 1 12 6.5 490 48* 44 15 30 1 10 5.7590 49* 42 0 30 1 27 6.6 115 50 42 1 30 1 26 7.9 125 51 42 2 30 1 25 8.2160 52 42 5 30 1 22 8.2 205 53 42 7.5 30 1 19.5 7.9 235 54 42 10 30 1 177.5 280 55* 42 13 30 1 14 6.7 340 56* 42 15 30 1 12 5.9 420 57* 40 0 301 29 6.5 100 58 40 1 30 1 28 7.9 108 59 40 2 30 1 27 8 130 60 40 5 30 124 8 160 61 40 7.5 30 1 21.5 7.8 185 62 40 10 30 1 19 7.3 215 63* 40 1330 1 16 6.5 260 64* 40 15 30 1 14 5.8 320 65* 35 0 30 1 34 6.1 80 66 351 30 1 33 7.7 85 67 35 2 30 1 32 8 94 68 35 5 30 1 29 8 110 69 35 7.5 301 26.5 7.5 125 70 35 10 30 1 24 7 150 71* 35 13 30 1 21 6.2 180 72* 3515 30 1 19 5.7 235 73* 30 0 30 1 39 5.7 65 74 30 1 30 1 38 7.3 69 75 302 30 1 37 7.7 75 76 30 5 30 1 34 7.4 85 77 30 7.5 30 1 31.5 7.1 95 78*30 10 30 1 29 6.7 110 79* 30 13 30 1 26 6 130 80* 30 15 30 1 24 5.3 175*out of the scope of the disclosure (claim 1)

TABLE 3 Electric properties Specific Magnetic resistance perme- SampleFerrite composition (mol %) logρ, ability No. Fe₂O₃ Mn₂O₃ ZnO CuO NiO ρ:Ω · cm μ (—) 81* 25 0 30 1 44 5.2 51 82  25 1 30 1 43 7 54 83  25 2 30 142 7.3 59 84  25 5 30 1 39 7.1 67 85  25 7.5 30 1 36.5 7 73 86* 25 10 301 34 6.4 88 87* 25 13 30 1 31 5.6 105 88* 25 15 30 1 29 4.9 140 89* 20 030 1 49 4.6 35 90* 20 1 30 1 48 6.2 38 91* 20 2 30 1 47 6.7 42 92* 20 530 1 44 6.3 50 93* 20 7.5 30 1 41.5 5.9 55 94* 20 10 30 1 39 5.6 70 95*20 13 30 1 36 5 87 96* 20 15 30 1 34 4.4 120 97* 15 0 30 1 54 3.9 18 98*15 1 30 1 53 5.4 20 99* 15 2 30 1 52 5.8 25 100*  15 5 30 1 49 5.4 33101*  15 7.5 30 1 46.5 5 40 102*  15 10 30 1 44 4.5 55 103*  15 13 30 141 3.8 70 104*  15 15 30 1 39 3.2 100 *out of the scope of thedisclosure (claim 1)

With respect to each of samples Nos. 1 to 17, 22 to 25, 30 to 33, 39 to41, 47 to 49, 55 to 57, 63 to 65, 71 to 73, 78 to 81 and 86 to 104, thespecific resistance log ρ was as small as less than 7 and desiredinsulation performance could not be achieved, since the composition waslocated in the outside of the shaded area (X) in FIG. 1.

On the contrary, with respect to each of samples Nos. 18 to 21, 26 to29, 34 to 38, 42 to 46, 50 to 54, 58 to 62, 66 to 70, 74 to 77 and 82 to85, it was found that the specific resistance log ρ was 7 or more, goodinsulation performance could be achieved, and a practically satisfactorylevel of magnetic permeability (μ), i.e., 50 or more, could be achieved,since the composition was located within the shaded area (X) in FIG. 1.

Example 2

Ceramic raw materials were weighed precisely in such a manner that themolar content of Fe₂O₃ was 44 mol % and the molar content of Mn₂O₃ was 5mol % (which fall within the ranges defined in the present disclosure),the molar content of ZnO was 30 mol %, the molar content of CuO wasvaried, and the remainder was made up by NiO, as shown in Table 4.Except for this matter, the same methods and procedures as in Example 1were performed, thereby producing ring-shaped samples Nos. 201 to 209and specific resistance measurement samples Nos. 201 to 209.

Subsequently, with respect to samples Nos. 201 to 209, specificresistance log ρ and magnetic permeability were determined by the samemethod and procedures as in Example 1.

In Table 4, the ferrite compositions and the measurement results forSample Nos. 201 to 209 are shown.

TABLE 4 Electric properties Specific Sam- resistance Magnetic pleFerrite composition (mol %) logρ, permeability No. Fe₂O₃ Mn₂O₃ ZnO CuONiO ρ: Ω · cm μ (—) 201 44 5 30 0 21 7.8 210 202 44 5 30 1 20 8 280 20344 5 30 2 19 8.2 310 204 44 5 30 3 18 7.9 325 205 44 5 30 4 17 7.5 310206 44 5 30 5 16 7.1 315 207* 44 5 30 6 15 6.1 320 208* 44 5 30 7 14 4.9300 209* 44 5 30 8 13 4.1 305 *out of the scope of the disclosure (claim1)

With respect to each of samples Nos. 207 to 209, the specific resistancelog ρ was as small as less than 7 and desired insulation performancecould not be achieved, since the molar content of CuO exceeded 5 mol %.

On the contrary, with respect to each of samples Nos. 201 to 206, suchgood results were obtained that the specific resistance log ρ was 7 ormore, good insulation performance could be achieved, and the magneticpermeability (μ) was 210 or more, since the molar content of CuO was 0to 5 mol % which falls within the range defined in the presentdisclosure.

Example 3

The same methods and procedures as in Example 1 were performed, exceptthat ceramic raw materials were weighed precisely in such a manner thatthe molar content of Fe₂O₃ was 44 mol %, the molar content of Mn₂O₃ was5 mol % and the molar content of CuO was 1 mol % (which fall within theranges defined in the present disclosure), the molar content of ZnO wasvaried, and the remainder was made up by NiO, as shown in Table 5. Inthis manner, ring-shaped samples Nos. 301 to 309 and specific resistancemeasurement samples Nos. 301 to 309 were produced.

With respect to each of samples Nos. 301 to 309, a specific resistancelog ρ and a magnetic permeability were determined by the same methodsand procedures as in Example 1.

With respect to each of samples Nos. 301 to 309, the temperaturedependency of saturation magnetization was determined by applying amagnetic field of 1 T (tesla) using a vibrating sample magnetometer(Toei Industry Co., Ltd.; model VSM-5-15). A Curie point (Tc) wasdetermined from the result of the temperature dependency of saturationmagnetization.

In Table 5, the ferrite compositions and the measurement results forSample Nos. 301 to 309 are shown.

TABLE 5 Electric properties Spe- Mag- cific netic resis- per- tance mea-Curie Ferrite composition logρ, bility point Sample (mol %) ρ: μ Tc No.Fe₂O₃ Mn₂O₃ ZnO CuO NiO Ω · cm (—) (° C.) 301*** 44 5 1 1 49 7.1 15 550302*** 44 5 3 1 47 7.3 20 515 303 44 5 6 1 44 7.4 35 465 304 44 5 10 140 7.6 55 420 305 44 5 15 1 35 7.6 110 340 306 44 5 25 1 25 7.7 230 275307 44 5 30 1 20 8 300 165 308 44 5 33 1 17 8.1 355 130 309** 44 5 35 115 8 400 110 **out of the scope of the disclosure (claim 2) ***out ofthe scope of the disclosure (claim 3)

With respect to sample No. 309, it was found that the Curie point (Tc)was 110° C. which was lower than those of other samples since the molarcontent of ZnO exceeded 33 mol %, although the specific resistance log ρand the magnetic permeability (μ) were satisfactory.

With respect to each of samples Nos. 301 and 302, the magneticpermeability (μ) was decreased to 20 or less since the molar content ofZnO was less than 6 mol %, although the specific resistance log ρ andthe Curie point (Tc) were satisfactory.

On the contrary, with respect to each of samples Nos. 303 to 308, it wasfound that the Curie point (Tc) was 130° C. or higher and therefore theoperation under high temperatures around 130° C. was ensured, and themagnetic permeability (μ) was 35 or more which was practicallyapplicable, since the molar content of ZnO was 6 to 33 mol %.

From the above-mentioned results, it was confirmed that the magneticpermeability (μ) was increased when the molar content of ZnO wasincreased and the Curie point (Tc) was decreased when the molar contentof ZnO was increased to be in excess.

Example 4

Two types of laminated inductors (samples Nos. 1′ and 27′) were producedrespectively using two types of magnetic material sheets, i.e., magneticmaterial sheets each having the same composition as that of sample No. 1produced in Example 1 and magnetic material sheets each having the samecomposition as that of sample No. 27 produced in Example 1. (See FIGS. 2to 4).

That is, magnetic material sheets each having the same composition asthat of sample No. 1 and magnetic material sheets each having the samecomposition as that of sample No. 27 were prepared. With respect to eachtype of the magnetic material sheets, the magnetic material sheets werelaminated together to form a first magnetic material layer. On the uppersurface of the first magnetic material layer, a Cu wire having adiameter of 100 μm was placed on substantially the center of the firstmagnetic material layer in parallel with the side surface of the firstmagnetic material layer. On the surface of the first magnetic materiallayer having the Cu wire placed thereon, multiple pieces of the magneticmaterial sheets were laminated to form a second magnetic material layer.Subsequently, the resultant product was heated to 60° C., and was thencompressed by applying a pressure of 100 MPa for 60 seconds. Thecompressed product was cut into a predetermined size, thereby forming alaminated molding.

Subsequently, the laminated molding was fully defatted at a temperatureof 600° C. in an atmosphere of which the oxygen partial pressure wasadjusted to 1.0×10⁻¹⁵ Pa so as to avoid the oxidation of Cu. Thedefatted laminated molding was introduced into a firing furnace in whichthe atmosphere had been adjusted to 6.7×10⁻² Pa with an N₂—H₂—H₂O mixedgas, and was then fired at 1,000° C. for 2 hours. In this manner, asintered ceramic body in which the Cu wire was embedded in the magneticbody part was produced.

Subsequently, a portion of the Cu wire which protruded from the endsurface of the sintered ceramic body was scraped off using a sand blastor a grinder, thereby producing a component body.

Subsequently, an electrically conductive paste for external electrodeswhich contained Cu or the like as the main component, was applied toboth ends of the component body (1), the resultant product was dried andthen baked at 900° C. to form external electrodes. The resultant productwas subjected to electroplating, thereby forming an Ni coating film andan Sn coating film on the surface of each of the external electrodes. Inthis manner, laminated inductor samples Nos. 1′ and 27′ were produced.

Each of samples Nos. 1′ and 27′ had an outer size of 1.6 mm in length,0.8 mm in width and 0.8 mm in thickness.

Subsequently, with respect to each of samples Nos. 1′ and 27′, animpedance property was measured using the impedance analyzer used inExample 1.

In FIG. 9, the measurement results are shown. A solid line indicates theimpedance property of sample No. 27′, which is a sample according to thepresent disclosure, and a dashed line indicates the impedance propertyof sample No. 1′, which is a sample that is out of the scope of thepresent disclosure. In the graph, frequencies (MHz) were plotted on theabscissa axis and values of impedance (Ω) were plotted on the ordinateaxis.

Sample No. 1′ had a specific resistance log ρ of as low as 2.8, andtherefore was out of the scope of the present disclosure. Therefore, thehighest value of impedance was about 15Ω, and a high level of impedancecould not be achieved.

On the contrary, sample No. 27′ has a specific resistance log ρ of 7.6which was sufficiently high, and was within the scope of the presentdisclosure. Therefore, high impedance could be achieved (i.e., thehighest value of impedance was about 50Ω) and a bell-shaped high anddesired impedance pattern could be obtained in a specific frequencyregion.

As mentioned above, the ferrite material can exhibit good insulationperformance even when the ferrite material having, embedded therein, anelectrically conductive material containing Cu as the main component.Therefore, it becomes possible to provide a ceramic electroniccomponent, such as an inductor, having good insulation performance andgood electric properties by using the ferrite material.

In a ferrite ceramic composition according to the present disclosure,the molar content of Cu is 0 to 5 mol % in terms of CuO content and,when the molar content (x (mol %)) of Fe in terms of Fe₂O₃ content andthe molar content (y (mol %)) of Mn in terms of Mn₂O₃ content areexpressed by a coordinate point (x,y), the coordinate point (x,y) islocated in an area bounded by the above-mentioned coordinate points A toH. Therefore, when the ferrite ceramic composition having a Cu-basedmaterial embedded therein is fired, the occurrence of the oxidation ofCu or the reduction of Fe₂O₃ can be prevented and, therefore, desiredinsulation performance can be secured without causing the decrease in aspecific resistance ρ.

Specifically, such good insulation performance that the specificresistance ρ is 10⁷ Ω·cm or more can be achieved. Consequently, itbecomes possible to produce a desired ceramic electronic componenthaving good electric properties including an impedance property.

Since the molar content of Zn is 33 mol % or less in terms of ZnOcontent, a sufficient Curie point can be secured and therefore itbecomes possible to produce a ceramic electronic component which can beoperated under conditions including a high operation temperature.

Further, since the molar content of Zn is 6 mol % or more in terms ofZnO content, good magnetic permeability can be secured.

An embodiment of a ceramic electronic component according to the presentdisclosure includes a magnetic body part and a metal wire materialhaving a linear or spiral shape and embedded in the magnetic body part,where the metal wire material include an electrically conductivematerial containing Cu as the main component and the magnetic body partinclude any of the above-mentioned ferrite ceramic compositions (i.e.,those within the scope of the disclosure). Therefore, even when themagnetic body part having the metal wire material embedded therein isfired, the occurrence of the oxidation of Cu or the reduction of Fe₂O₃can be avoided, and it becomes possible to produce a ceramic electroniccomponent having a desired specific resistance ρ and good electricproperties.

Even when the magnetic body part having an electrically conductivematerial containing Cu as the main component embedded therein is firedin an atmosphere having an oxygen partial pressure equal to or lowerthan the equilibrium oxygen partial pressure for Cu—Cu₂O, the magneticbody part can be sintered without undergoing the oxidation of Cu or thereduction of Fe₂O₃. Therefore, it becomes possible to produce achip-type inductor having good electric properties as a ceramicelectronic component.

An embodiment of present disclosure includes a process for producing aceramic electronic component having a calcination step of weighing an Fecompound, an Mn compound, a Cu compound, a Zn compound and an Nicompound precisely in such a manner that a molar content of Cu becomes 0to 5 mol % in terms of CuO content and, when a molar content (x (mol %))of Fe in terms of Fe₂O₃ content and a molar content (y (mol %)) of Mn interms of Mn₂O₂ content are expressed by a coordinate point (x,y), thecoordinate point (x,y) can be located in a specific area bounded bycoordinate points A to H, mixing the weighed compounds together, andcalcining the resultant mixture, thereby producing a calcined powder; aceramic thin layer body production step of producing ceramic thin layerbodies from the calcined powder; a laminate formation step of laminatingthe multiple ceramic thin layer bodies on each other in such a mannerthat a metal wire material containing Cu as the main component andhaving a linear shape is intercalated between at least a pair of theceramic thin layer bodies, thereby forming a laminate; and a firing stepof firing the laminate in a firing atmosphere having an oxygen partialpressure equal to or lower than the equilibrium oxygen partial pressurefor Cu—Cu₂O. Therefore, even when the ferrite material is fired togetherwith a linear metal wire material containing Cu as the main component ina firing atmosphere having an oxygen partial pressure equal to or lowerthan the equilibrium oxygen partial pressure for Cu—Cu₂O, it becomespossible to produce a ceramic electronic component having goodinsulation performance and good electric properties without undergoingthe oxidation of Cu or the reduction of Fe.

An embodiment of present disclosure includes a process for producing aceramic electronic component having a calcination step of weighing an Fecompound, an Mn compound, a Cu compound, a Zn compound and an Nicompound precisely in such a manner that a molar content of Cu becomes 0to 5 mol % in terms of CuO content and, when a molar content (x (mol %))of Fe in terms of Fe₂O₃ content and a molar content (y (mol %)) of Mn interms of Mn₂O₂ content are expressed by a coordinate point (x,y), thecoordinate point (x,y) can be located in a specific area bounded bycoordinate points A to H, mixing the weighed compounds together, andcalcining the resultant mixture, thereby producing a calcined powder; aferrite paste production step of producing a ferrite paste from thecalcined powder; a molding production step of placing a metal wirematerial containing Cu as the main component in a mold, then injectingthe ferrite paste into the mold and carrying out a molding treatment toproduce a molding; and a firing step of firing the molding in a firingatmosphere having an oxygen partial pressure equal to or lower than theequilibrium oxygen partial pressure for Cu—Cu₂O. Therefore, as in theabove-mentioned case, it becomes possible to produce a ceramicelectronic component having good insulation performance and highreliability without undergoing the oxidation of Cu or the reduction ofFe.

1. A ferrite ceramic composition comprising at least Fe, Mn, Ni and Zn,wherein, in the ferrite ceramic composition, a molar content of Cu is 0to 5 mol % in terms of CuO content and, when a molar content (x (mol %))of Fe in terms of Fe₂O₃ content and a molar content (y (mol %)) of Mn interms of Mn₂O₃ content are expressed by a coordinate point (x,y), thecoordinate point (x,y) is located in an area bounded by coordinatepoints A (25,1), B (47,1), C (47,7.5), D (45,7.5), E (45,10), F (35,10),G (35,7.5) and H (25,7.5).
 2. The ferrite ceramic composition accordingto claim 1, wherein the molar content of Zn is 33 mol % or less in termsof ZnO content.
 3. The ferrite ceramic composition according to claim 1,wherein the molar content of Zn is 6 mol % or more in terms of ZnOcontent.
 4. The ferrite ceramic composition according to claim 2,wherein the molar content of Zn is 6 mol % or more in terms of ZnOcontent.
 5. A ceramic electronic component comprising a magnetic bodypart and a metal wire material embedded in the magnetic body part,wherein the metal wire material comprises an electrically conductivematerial containing Cu as the main component and the magnetic body partcomprises the ferrite ceramic composition claimed in claim
 1. 6. Theceramic electronic component according to claim 5, wherein the metalwire material has a linear shape.
 7. The ceramic electronic componentaccording to claim 5, wherein the metal wire material has a spiralshape.
 8. A ceramic electronic component comprising a magnetic body partand a metal wire material embedded in the magnetic body part, whereinthe metal wire material comprises an electrically conductive materialcontaining Cu as the main component and the magnetic body part comprisesthe ferrite ceramic composition claimed in claim
 2. 9. The ceramicelectronic component according to claim 8, wherein the metal wirematerial has a linear shape.
 10. The ceramic electronic componentaccording to claim 8, wherein the metal wire material has a spiralshape.
 11. A ceramic electronic component comprising a magnetic bodypart and a metal wire material embedded in the magnetic body part,wherein the metal wire material comprises an electrically conductivematerial containing Cu as the main component and the magnetic body partcomprises the ferrite ceramic composition claimed in claim
 3. 12. Theceramic electronic component according to claim 11, wherein the metalwire material has a linear shape.
 13. The ceramic electronic componentaccording to claim 11, wherein the metal wire material has a spiralshape.
 14. A ceramic electronic component comprising a magnetic bodypart and a metal wire material embedded in the magnetic body part,wherein the metal wire material comprises an electrically conductivematerial containing Cu as the main component and the magnetic body partcomprises the ferrite ceramic composition claimed in claim
 4. 15. Theceramic electronic component according to claim 14, wherein the metalwire material has a linear shape.
 16. The ceramic electronic componentaccording to claim 14, wherein the metal wire material has a spiralshape.
 17. The ceramic electronic component according to claim 5,wherein the magnetic body part is fired in an atmosphere having anoxygen partial pressure equal to or lower than the equilibrium oxygenpartial pressure for Cu—Cu₂O.
 18. A process for producing a ceramicelectronic component, comprising: a calcination step of weighing an Fecompound, an Mn compound, a Cu compound, a Zn compound and an Nicompound precisely in such a manner that a molar content of Cu becomes 0to 5 mol % in terms of CuO content and, when a molar content (x (mol %))of Fe in terms of Fe₂O₃ content and a molar content (y (mol %)) of Mn interms of Mn₂O₃ content are expressed by a coordinate point (x,y), thecoordinate point (x,y) can be located in an area bounded by coordinatepoints A (25,1), B (47,1), C (47,7.5), D (45,7.5), E (45,10), F (35,10),G (35,7.5) and H (25,7.5), mixing the weighed compounds together, andcalcining the resultant mixture, thereby producing a calcined powder; aceramic thin layer body production step of producing ceramic thin layerbodies from the calcined powder; a laminate formation step of laminatingthe multiple ceramic thin layer bodies on each other in such a mannerthat a metal wire material containing Cu as the main component andhaving a linear shape is intercalated between at least a pair of theceramic thin layer bodies, thereby forming a laminate; and a firing stepof firing the laminate in a firing atmosphere having an oxygen partialpressure equal to or lower than the equilibrium oxygen partial pressurefor Cu—Cu₂O.
 19. A process for producing a ceramic electronic component,comprising: a calcination step of weighing an Fe compound, an Mncompound, a Cu compound, a Zn compound and an Ni compound precisely insuch a manner that a molar content of Cu becomes 0 to 5 mol % in termsof CuO content and, when a molar content (x (mol %)) of Fe in terms ofFe₂O₃ content and the molar content (y (mol %)) of Mn in terms of Mn₂O₂content are expressed by a coordinate point (x,y), the coordinate point(x,y) can be located in an area bounded by coordinate points A (25,1), B(47,1), C (47,7.5), D (45,7.5), E (45,10), F (35,10), G (35,7.5) and H(25,7.5), mixing the weighed compounds together, and calcining theresultant mixture, thereby producing a calcined powder; a ferrite pasteproduction step of producing a ferrite paste from the calcined powder; amolding production step of placing a metal wire material containing Cuas the main component in a mold, then injecting the ferrite paste intothe mold and carrying out a molding treatment to produce a molding; anda firing step of firing the molding in a firing atmosphere having anoxygen partial pressure equal to or lower than the equilibrium oxygenpartial pressure for Cu—Cu₂O.